<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="generator" content="Asciidoctor 2.0.16">
<meta name="author" content="Daryle Walker, Beman Dawes, Glen Joseph Fernandes &lt;glenjofe@gmail.com&gt;">
<title>Boost.IO</title>
<link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Open+Sans:300,300italic,400,400italic,600,600italic%7CNoto+Serif:400,400italic,700,700italic%7CDroid+Sans+Mono:400,700">
<style>
/*! Asciidoctor default stylesheet | MIT License | https://asciidoctor.org */
/* Uncomment the following line when using as a custom stylesheet */
/* @import "https://fonts.googleapis.com/css?family=Open+Sans:300,300italic,400,400italic,600,600italic%7CNoto+Serif:400,400italic,700,700italic%7CDroid+Sans+Mono:400,700"; */
html{font-family:sans-serif;-webkit-text-size-adjust:100%}
a{background:none}
a:focus{outline:thin dotted}
a:active,a:hover{outline:0}
h1{font-size:2em;margin:.67em 0}
b,strong{font-weight:bold}
abbr{font-size:.9em}
abbr[title]{cursor:help;border-bottom:1px dotted #dddddf;text-decoration:none}
dfn{font-style:italic}
hr{height:0}
mark{background:#ff0;color:#000}
code,kbd,pre,samp{font-family:monospace;font-size:1em}
pre{white-space:pre-wrap}
q{quotes:"\201C" "\201D" "\2018" "\2019"}
small{font-size:80%}
sub,sup{font-size:75%;line-height:0;position:relative;vertical-align:baseline}
sup{top:-.5em}
sub{bottom:-.25em}
img{border:0}
svg:not(:root){overflow:hidden}
figure{margin:0}
audio,video{display:inline-block}
audio:not([controls]){display:none;height:0}
fieldset{border:1px solid silver;margin:0 2px;padding:.35em .625em .75em}
legend{border:0;padding:0}
button,input,select,textarea{font-family:inherit;font-size:100%;margin:0}
button,input{line-height:normal}
button,select{text-transform:none}
button,html input[type=button],input[type=reset],input[type=submit]{-webkit-appearance:button;cursor:pointer}
button[disabled],html input[disabled]{cursor:default}
input[type=checkbox],input[type=radio]{padding:0}
button::-moz-focus-inner,input::-moz-focus-inner{border:0;padding:0}
textarea{overflow:auto;vertical-align:top}
table{border-collapse:collapse;border-spacing:0}
*,::before,::after{box-sizing:border-box}
html,body{font-size:100%}
body{background:#fff;color:rgba(0,0,0,.8);padding:0;margin:0;font-family:"Noto Serif","DejaVu Serif",serif;line-height:1;position:relative;cursor:auto;-moz-tab-size:4;-o-tab-size:4;tab-size:4;word-wrap:anywhere;-moz-osx-font-smoothing:grayscale;-webkit-font-smoothing:antialiased}
a:hover{cursor:pointer}
img,object,embed{max-width:100%;height:auto}
object,embed{height:100%}
img{-ms-interpolation-mode:bicubic}
.left{float:left!important}
.right{float:right!important}
.text-left{text-align:left!important}
.text-right{text-align:right!important}
.text-center{text-align:center!important}
.text-justify{text-align:justify!important}
.hide{display:none}
img,object,svg{display:inline-block;vertical-align:middle}
textarea{height:auto;min-height:50px}
select{width:100%}
.subheader,.admonitionblock td.content>.title,.audioblock>.title,.exampleblock>.title,.imageblock>.title,.listingblock>.title,.literalblock>.title,.stemblock>.title,.openblock>.title,.paragraph>.title,.quoteblock>.title,table.tableblock>.title,.verseblock>.title,.videoblock>.title,.dlist>.title,.olist>.title,.ulist>.title,.qlist>.title,.hdlist>.title{line-height:1.45;color:#7a2518;font-weight:400;margin-top:0;margin-bottom:.25em}
div,dl,dt,dd,ul,ol,li,h1,h2,h3,#toctitle,.sidebarblock>.content>.title,h4,h5,h6,pre,form,p,blockquote,th,td{margin:0;padding:0}
a{color:#2156a5;text-decoration:underline;line-height:inherit}
a:hover,a:focus{color:#1d4b8f}
a img{border:0}
p{line-height:1.6;margin-bottom:1.25em;text-rendering:optimizeLegibility}
p aside{font-size:.875em;line-height:1.35;font-style:italic}
h1,h2,h3,#toctitle,.sidebarblock>.content>.title,h4,h5,h6{font-family:"Open Sans","DejaVu Sans",sans-serif;font-weight:300;font-style:normal;color:#ba3925;text-rendering:optimizeLegibility;margin-top:1em;margin-bottom:.5em;line-height:1.0125em}
h1 small,h2 small,h3 small,#toctitle small,.sidebarblock>.content>.title small,h4 small,h5 small,h6 small{font-size:60%;color:#e99b8f;line-height:0}
h1{font-size:2.125em}
h2{font-size:1.6875em}
h3,#toctitle,.sidebarblock>.content>.title{font-size:1.375em}
h4,h5{font-size:1.125em}
h6{font-size:1em}
hr{border:solid #dddddf;border-width:1px 0 0;clear:both;margin:1.25em 0 1.1875em}
em,i{font-style:italic;line-height:inherit}
strong,b{font-weight:bold;line-height:inherit}
small{font-size:60%;line-height:inherit}
code{font-family:"Droid Sans Mono","DejaVu Sans Mono",monospace;font-weight:400;color:rgba(0,0,0,.9)}
ul,ol,dl{line-height:1.6;margin-bottom:1.25em;list-style-position:outside;font-family:inherit}
ul,ol{margin-left:1.5em}
ul li ul,ul li ol{margin-left:1.25em;margin-bottom:0}
ul.square li ul,ul.circle li ul,ul.disc li ul{list-style:inherit}
ul.square{list-style-type:square}
ul.circle{list-style-type:circle}
ul.disc{list-style-type:disc}
ol li ul,ol li ol{margin-left:1.25em;margin-bottom:0}
dl dt{margin-bottom:.3125em;font-weight:bold}
dl dd{margin-bottom:1.25em}
blockquote{margin:0 0 1.25em;padding:.5625em 1.25em 0 1.1875em;border-left:1px solid #ddd}
blockquote,blockquote p{line-height:1.6;color:rgba(0,0,0,.85)}
@media screen and (min-width:768px){h1,h2,h3,#toctitle,.sidebarblock>.content>.title,h4,h5,h6{line-height:1.2}
h1{font-size:2.75em}
h2{font-size:2.3125em}
h3,#toctitle,.sidebarblock>.content>.title{font-size:1.6875em}
h4{font-size:1.4375em}}
table{background:#fff;margin-bottom:1.25em;border:1px solid #dedede;word-wrap:normal}
table thead,table tfoot{background:#f7f8f7}
table thead tr th,table thead tr td,table tfoot tr th,table tfoot tr td{padding:.5em .625em .625em;font-size:inherit;color:rgba(0,0,0,.8);text-align:left}
table tr th,table tr td{padding:.5625em .625em;font-size:inherit;color:rgba(0,0,0,.8)}
table tr.even,table tr.alt{background:#f8f8f7}
table thead tr th,table tfoot tr th,table tbody tr td,table tr td,table tfoot tr td{line-height:1.6}
h1,h2,h3,#toctitle,.sidebarblock>.content>.title,h4,h5,h6{line-height:1.2;word-spacing:-.05em}
h1 strong,h2 strong,h3 strong,#toctitle strong,.sidebarblock>.content>.title strong,h4 strong,h5 strong,h6 strong{font-weight:400}
.center{margin-left:auto;margin-right:auto}
.stretch{width:100%}
.clearfix::before,.clearfix::after,.float-group::before,.float-group::after{content:" ";display:table}
.clearfix::after,.float-group::after{clear:both}
:not(pre).nobreak{word-wrap:normal}
:not(pre).nowrap{white-space:nowrap}
:not(pre).pre-wrap{white-space:pre-wrap}
:not(pre):not([class^=L])>code{font-size:.9375em;font-style:normal!important;letter-spacing:0;padding:.1em .5ex;word-spacing:-.15em;background:#f7f7f8;border-radius:4px;line-height:1.45;text-rendering:optimizeSpeed}
pre{color:rgba(0,0,0,.9);font-family:"Droid Sans Mono","DejaVu Sans Mono",monospace;line-height:1.45;text-rendering:optimizeSpeed}
pre code,pre pre{color:inherit;font-size:inherit;line-height:inherit}
pre>code{display:block}
pre.nowrap,pre.nowrap pre{white-space:pre;word-wrap:normal}
em em{font-style:normal}
strong strong{font-weight:400}
.keyseq{color:rgba(51,51,51,.8)}
kbd{font-family:"Droid Sans Mono","DejaVu Sans Mono",monospace;display:inline-block;color:rgba(0,0,0,.8);font-size:.65em;line-height:1.45;background:#f7f7f7;border:1px solid #ccc;border-radius:3px;box-shadow:0 1px 0 rgba(0,0,0,.2),inset 0 0 0 .1em #fff;margin:0 .15em;padding:.2em .5em;vertical-align:middle;position:relative;top:-.1em;white-space:nowrap}
.keyseq kbd:first-child{margin-left:0}
.keyseq kbd:last-child{margin-right:0}
.menuseq,.menuref{color:#000}
.menuseq b:not(.caret),.menuref{font-weight:inherit}
.menuseq{word-spacing:-.02em}
.menuseq b.caret{font-size:1.25em;line-height:.8}
.menuseq i.caret{font-weight:bold;text-align:center;width:.45em}
b.button::before,b.button::after{position:relative;top:-1px;font-weight:400}
b.button::before{content:"[";padding:0 3px 0 2px}
b.button::after{content:"]";padding:0 2px 0 3px}
p a>code:hover{color:rgba(0,0,0,.9)}
#header,#content,#footnotes,#footer{width:100%;margin:0 auto;max-width:62.5em;*zoom:1;position:relative;padding-left:.9375em;padding-right:.9375em}
#header::before,#header::after,#content::before,#content::after,#footnotes::before,#footnotes::after,#footer::before,#footer::after{content:" ";display:table}
#header::after,#content::after,#footnotes::after,#footer::after{clear:both}
#content{margin-top:1.25em}
#content::before{content:none}
#header>h1:first-child{color:rgba(0,0,0,.85);margin-top:2.25rem;margin-bottom:0}
#header>h1:first-child+#toc{margin-top:8px;border-top:1px solid #dddddf}
#header>h1:only-child,body.toc2 #header>h1:nth-last-child(2){border-bottom:1px solid #dddddf;padding-bottom:8px}
#header .details{border-bottom:1px solid #dddddf;line-height:1.45;padding-top:.25em;padding-bottom:.25em;padding-left:.25em;color:rgba(0,0,0,.6);display:flex;flex-flow:row wrap}
#header .details span:first-child{margin-left:-.125em}
#header .details span.email a{color:rgba(0,0,0,.85)}
#header .details br{display:none}
#header .details br+span::before{content:"\00a0\2013\00a0"}
#header .details br+span.author::before{content:"\00a0\22c5\00a0";color:rgba(0,0,0,.85)}
#header .details br+span#revremark::before{content:"\00a0|\00a0"}
#header #revnumber{text-transform:capitalize}
#header #revnumber::after{content:"\00a0"}
#content>h1:first-child:not([class]){color:rgba(0,0,0,.85);border-bottom:1px solid #dddddf;padding-bottom:8px;margin-top:0;padding-top:1rem;margin-bottom:1.25rem}
#toc{border-bottom:1px solid #e7e7e9;padding-bottom:.5em}
#toc>ul{margin-left:.125em}
#toc ul.sectlevel0>li>a{font-style:italic}
#toc ul.sectlevel0 ul.sectlevel1{margin:.5em 0}
#toc ul{font-family:"Open Sans","DejaVu Sans",sans-serif;list-style-type:none}
#toc li{line-height:1.3334;margin-top:.3334em}
#toc a{text-decoration:none}
#toc a:active{text-decoration:underline}
#toctitle{color:#7a2518;font-size:1.2em}
@media screen and (min-width:768px){#toctitle{font-size:1.375em}
body.toc2{padding-left:15em;padding-right:0}
#toc.toc2{margin-top:0!important;background:#f8f8f7;position:fixed;width:15em;left:0;top:0;border-right:1px solid #e7e7e9;border-top-width:0!important;border-bottom-width:0!important;z-index:1000;padding:1.25em 1em;height:100%;overflow:auto}
#toc.toc2 #toctitle{margin-top:0;margin-bottom:.8rem;font-size:1.2em}
#toc.toc2>ul{font-size:.9em;margin-bottom:0}
#toc.toc2 ul ul{margin-left:0;padding-left:1em}
#toc.toc2 ul.sectlevel0 ul.sectlevel1{padding-left:0;margin-top:.5em;margin-bottom:.5em}
body.toc2.toc-right{padding-left:0;padding-right:15em}
body.toc2.toc-right #toc.toc2{border-right-width:0;border-left:1px solid #e7e7e9;left:auto;right:0}}
@media screen and (min-width:1280px){body.toc2{padding-left:20em;padding-right:0}
#toc.toc2{width:20em}
#toc.toc2 #toctitle{font-size:1.375em}
#toc.toc2>ul{font-size:.95em}
#toc.toc2 ul ul{padding-left:1.25em}
body.toc2.toc-right{padding-left:0;padding-right:20em}}
#content #toc{border:1px solid #e0e0dc;margin-bottom:1.25em;padding:1.25em;background:#f8f8f7;border-radius:4px}
#content #toc>:first-child{margin-top:0}
#content #toc>:last-child{margin-bottom:0}
#footer{max-width:none;background:rgba(0,0,0,.8);padding:1.25em}
#footer-text{color:hsla(0,0%,100%,.8);line-height:1.44}
#content{margin-bottom:.625em}
.sect1{padding-bottom:.625em}
@media screen and (min-width:768px){#content{margin-bottom:1.25em}
.sect1{padding-bottom:1.25em}}
.sect1:last-child{padding-bottom:0}
.sect1+.sect1{border-top:1px solid #e7e7e9}
#content h1>a.anchor,h2>a.anchor,h3>a.anchor,#toctitle>a.anchor,.sidebarblock>.content>.title>a.anchor,h4>a.anchor,h5>a.anchor,h6>a.anchor{position:absolute;z-index:1001;width:1.5ex;margin-left:-1.5ex;display:block;text-decoration:none!important;visibility:hidden;text-align:center;font-weight:400}
#content h1>a.anchor::before,h2>a.anchor::before,h3>a.anchor::before,#toctitle>a.anchor::before,.sidebarblock>.content>.title>a.anchor::before,h4>a.anchor::before,h5>a.anchor::before,h6>a.anchor::before{content:"\00A7";font-size:.85em;display:block;padding-top:.1em}
#content h1:hover>a.anchor,#content h1>a.anchor:hover,h2:hover>a.anchor,h2>a.anchor:hover,h3:hover>a.anchor,#toctitle:hover>a.anchor,.sidebarblock>.content>.title:hover>a.anchor,h3>a.anchor:hover,#toctitle>a.anchor:hover,.sidebarblock>.content>.title>a.anchor:hover,h4:hover>a.anchor,h4>a.anchor:hover,h5:hover>a.anchor,h5>a.anchor:hover,h6:hover>a.anchor,h6>a.anchor:hover{visibility:visible}
#content h1>a.link,h2>a.link,h3>a.link,#toctitle>a.link,.sidebarblock>.content>.title>a.link,h4>a.link,h5>a.link,h6>a.link{color:#ba3925;text-decoration:none}
#content h1>a.link:hover,h2>a.link:hover,h3>a.link:hover,#toctitle>a.link:hover,.sidebarblock>.content>.title>a.link:hover,h4>a.link:hover,h5>a.link:hover,h6>a.link:hover{color:#a53221}
details,.audioblock,.imageblock,.literalblock,.listingblock,.stemblock,.videoblock{margin-bottom:1.25em}
details{margin-left:1.25rem}
details>summary{cursor:pointer;display:block;position:relative;line-height:1.6;margin-bottom:.625rem;-webkit-tap-highlight-color:transparent}
details>summary::before{content:"";border:solid transparent;border-left:solid;border-width:.3em 0 .3em .5em;position:absolute;top:.5em;left:-1.25rem;transform:translateX(15%)}
details[open]>summary::before{border:solid transparent;border-top:solid;border-width:.5em .3em 0;transform:translateY(15%)}
details>summary::after{content:"";width:1.25rem;height:1em;position:absolute;top:.3em;left:-1.25rem}
.admonitionblock td.content>.title,.audioblock>.title,.exampleblock>.title,.imageblock>.title,.listingblock>.title,.literalblock>.title,.stemblock>.title,.openblock>.title,.paragraph>.title,.quoteblock>.title,table.tableblock>.title,.verseblock>.title,.videoblock>.title,.dlist>.title,.olist>.title,.ulist>.title,.qlist>.title,.hdlist>.title{text-rendering:optimizeLegibility;text-align:left;font-family:"Noto Serif","DejaVu Serif",serif;font-size:1rem;font-style:italic}
table.tableblock.fit-content>caption.title{white-space:nowrap;width:0}
.paragraph.lead>p,#preamble>.sectionbody>[class=paragraph]:first-of-type p{font-size:1.21875em;line-height:1.6;color:rgba(0,0,0,.85)}
.admonitionblock>table{border-collapse:separate;border:0;background:none;width:100%}
.admonitionblock>table td.icon{text-align:center;width:80px}
.admonitionblock>table td.icon img{max-width:none}
.admonitionblock>table td.icon .title{font-weight:bold;font-family:"Open Sans","DejaVu Sans",sans-serif;text-transform:uppercase}
.admonitionblock>table td.content{padding-left:1.125em;padding-right:1.25em;border-left:1px solid #dddddf;color:rgba(0,0,0,.6);word-wrap:anywhere}
.admonitionblock>table td.content>:last-child>:last-child{margin-bottom:0}
.exampleblock>.content{border:1px solid #e6e6e6;margin-bottom:1.25em;padding:1.25em;background:#fff;border-radius:4px}
.exampleblock>.content>:first-child{margin-top:0}
.exampleblock>.content>:last-child{margin-bottom:0}
.sidebarblock{border:1px solid #dbdbd6;margin-bottom:1.25em;padding:1.25em;background:#f3f3f2;border-radius:4px}
.sidebarblock>:first-child{margin-top:0}
.sidebarblock>:last-child{margin-bottom:0}
.sidebarblock>.content>.title{color:#7a2518;margin-top:0;text-align:center}
.exampleblock>.content>:last-child>:last-child,.exampleblock>.content .olist>ol>li:last-child>:last-child,.exampleblock>.content .ulist>ul>li:last-child>:last-child,.exampleblock>.content .qlist>ol>li:last-child>:last-child,.sidebarblock>.content>:last-child>:last-child,.sidebarblock>.content .olist>ol>li:last-child>:last-child,.sidebarblock>.content .ulist>ul>li:last-child>:last-child,.sidebarblock>.content .qlist>ol>li:last-child>:last-child{margin-bottom:0}
.literalblock pre,.listingblock>.content>pre{border-radius:4px;overflow-x:auto;padding:1em;font-size:.8125em}
@media screen and (min-width:768px){.literalblock pre,.listingblock>.content>pre{font-size:.90625em}}
@media screen and (min-width:1280px){.literalblock pre,.listingblock>.content>pre{font-size:1em}}
.literalblock pre,.listingblock>.content>pre:not(.highlight),.listingblock>.content>pre[class=highlight],.listingblock>.content>pre[class^="highlight "]{background:#f7f7f8}
.literalblock.output pre{color:#f7f7f8;background:rgba(0,0,0,.9)}
.listingblock>.content{position:relative}
.listingblock code[data-lang]::before{display:none;content:attr(data-lang);position:absolute;font-size:.75em;top:.425rem;right:.5rem;line-height:1;text-transform:uppercase;color:inherit;opacity:.5}
.listingblock:hover code[data-lang]::before{display:block}
.listingblock.terminal pre .command::before{content:attr(data-prompt);padding-right:.5em;color:inherit;opacity:.5}
.listingblock.terminal pre .command:not([data-prompt])::before{content:"$"}
.listingblock pre.highlightjs{padding:0}
.listingblock pre.highlightjs>code{padding:1em;border-radius:4px}
.listingblock pre.prettyprint{border-width:0}
.prettyprint{background:#f7f7f8}
pre.prettyprint .linenums{line-height:1.45;margin-left:2em}
pre.prettyprint li{background:none;list-style-type:inherit;padding-left:0}
pre.prettyprint li code[data-lang]::before{opacity:1}
pre.prettyprint li:not(:first-child) code[data-lang]::before{display:none}
table.linenotable{border-collapse:separate;border:0;margin-bottom:0;background:none}
table.linenotable td[class]{color:inherit;vertical-align:top;padding:0;line-height:inherit;white-space:normal}
table.linenotable td.code{padding-left:.75em}
table.linenotable td.linenos{border-right:1px solid;opacity:.35;padding-right:.5em}
pre.pygments .lineno{border-right:1px solid;opacity:.35;display:inline-block;margin-right:.75em}
pre.pygments .lineno::before{content:"";margin-right:-.125em}
.quoteblock{margin:0 1em 1.25em 1.5em;display:table}
.quoteblock:not(.excerpt)>.title{margin-left:-1.5em;margin-bottom:.75em}
.quoteblock blockquote,.quoteblock p{color:rgba(0,0,0,.85);font-size:1.15rem;line-height:1.75;word-spacing:.1em;letter-spacing:0;font-style:italic;text-align:justify}
.quoteblock blockquote{margin:0;padding:0;border:0}
.quoteblock blockquote::before{content:"\201c";float:left;font-size:2.75em;font-weight:bold;line-height:.6em;margin-left:-.6em;color:#7a2518;text-shadow:0 1px 2px rgba(0,0,0,.1)}
.quoteblock blockquote>.paragraph:last-child p{margin-bottom:0}
.quoteblock .attribution{margin-top:.75em;margin-right:.5ex;text-align:right}
.verseblock{margin:0 1em 1.25em}
.verseblock pre{font-family:"Open Sans","DejaVu Sans",sans-serif;font-size:1.15rem;color:rgba(0,0,0,.85);font-weight:300;text-rendering:optimizeLegibility}
.verseblock pre strong{font-weight:400}
.verseblock .attribution{margin-top:1.25rem;margin-left:.5ex}
.quoteblock .attribution,.verseblock .attribution{font-size:.9375em;line-height:1.45;font-style:italic}
.quoteblock .attribution br,.verseblock .attribution br{display:none}
.quoteblock .attribution cite,.verseblock .attribution cite{display:block;letter-spacing:-.025em;color:rgba(0,0,0,.6)}
.quoteblock.abstract blockquote::before,.quoteblock.excerpt blockquote::before,.quoteblock .quoteblock blockquote::before{display:none}
.quoteblock.abstract blockquote,.quoteblock.abstract p,.quoteblock.excerpt blockquote,.quoteblock.excerpt p,.quoteblock .quoteblock blockquote,.quoteblock .quoteblock p{line-height:1.6;word-spacing:0}
.quoteblock.abstract{margin:0 1em 1.25em;display:block}
.quoteblock.abstract>.title{margin:0 0 .375em;font-size:1.15em;text-align:center}
.quoteblock.excerpt>blockquote,.quoteblock .quoteblock{padding:0 0 .25em 1em;border-left:.25em solid #dddddf}
.quoteblock.excerpt,.quoteblock .quoteblock{margin-left:0}
.quoteblock.excerpt blockquote,.quoteblock.excerpt p,.quoteblock .quoteblock blockquote,.quoteblock .quoteblock p{color:inherit;font-size:1.0625rem}
.quoteblock.excerpt .attribution,.quoteblock .quoteblock .attribution{color:inherit;font-size:.85rem;text-align:left;margin-right:0}
p.tableblock:last-child{margin-bottom:0}
td.tableblock>.content{margin-bottom:1.25em;word-wrap:anywhere}
td.tableblock>.content>:last-child{margin-bottom:-1.25em}
table.tableblock,th.tableblock,td.tableblock{border:0 solid #dedede}
table.grid-all>*>tr>*{border-width:1px}
table.grid-cols>*>tr>*{border-width:0 1px}
table.grid-rows>*>tr>*{border-width:1px 0}
table.frame-all{border-width:1px}
table.frame-ends{border-width:1px 0}
table.frame-sides{border-width:0 1px}
table.frame-none>colgroup+*>:first-child>*,table.frame-sides>colgroup+*>:first-child>*{border-top-width:0}
table.frame-none>:last-child>:last-child>*,table.frame-sides>:last-child>:last-child>*{border-bottom-width:0}
table.frame-none>*>tr>:first-child,table.frame-ends>*>tr>:first-child{border-left-width:0}
table.frame-none>*>tr>:last-child,table.frame-ends>*>tr>:last-child{border-right-width:0}
table.stripes-all tr,table.stripes-odd tr:nth-of-type(odd),table.stripes-even tr:nth-of-type(even),table.stripes-hover tr:hover{background:#f8f8f7}
th.halign-left,td.halign-left{text-align:left}
th.halign-right,td.halign-right{text-align:right}
th.halign-center,td.halign-center{text-align:center}
th.valign-top,td.valign-top{vertical-align:top}
th.valign-bottom,td.valign-bottom{vertical-align:bottom}
th.valign-middle,td.valign-middle{vertical-align:middle}
table thead th,table tfoot th{font-weight:bold}
tbody tr th{background:#f7f8f7}
tbody tr th,tbody tr th p,tfoot tr th,tfoot tr th p{color:rgba(0,0,0,.8);font-weight:bold}
p.tableblock>code:only-child{background:none;padding:0}
p.tableblock{font-size:1em}
ol{margin-left:1.75em}
ul li ol{margin-left:1.5em}
dl dd{margin-left:1.125em}
dl dd:last-child,dl dd:last-child>:last-child{margin-bottom:0}
ol>li p,ul>li p,ul dd,ol dd,.olist .olist,.ulist .ulist,.ulist .olist,.olist .ulist{margin-bottom:.625em}
ul.checklist,ul.none,ol.none,ul.no-bullet,ol.no-bullet,ol.unnumbered,ul.unstyled,ol.unstyled{list-style-type:none}
ul.no-bullet,ol.no-bullet,ol.unnumbered{margin-left:.625em}
ul.unstyled,ol.unstyled{margin-left:0}
ul.checklist>li>p:first-child{margin-left:-1em}
ul.checklist>li>p:first-child>.fa-square-o:first-child,ul.checklist>li>p:first-child>.fa-check-square-o:first-child{width:1.25em;font-size:.8em;position:relative;bottom:.125em}
ul.checklist>li>p:first-child>input[type=checkbox]:first-child{margin-right:.25em}
ul.inline{display:flex;flex-flow:row wrap;list-style:none;margin:0 0 .625em -1.25em}
ul.inline>li{margin-left:1.25em}
.unstyled dl dt{font-weight:400;font-style:normal}
ol.arabic{list-style-type:decimal}
ol.decimal{list-style-type:decimal-leading-zero}
ol.loweralpha{list-style-type:lower-alpha}
ol.upperalpha{list-style-type:upper-alpha}
ol.lowerroman{list-style-type:lower-roman}
ol.upperroman{list-style-type:upper-roman}
ol.lowergreek{list-style-type:lower-greek}
.hdlist>table,.colist>table{border:0;background:none}
.hdlist>table>tbody>tr,.colist>table>tbody>tr{background:none}
td.hdlist1,td.hdlist2{vertical-align:top;padding:0 .625em}
td.hdlist1{font-weight:bold;padding-bottom:1.25em}
td.hdlist2{word-wrap:anywhere}
.literalblock+.colist,.listingblock+.colist{margin-top:-.5em}
.colist td:not([class]):first-child{padding:.4em .75em 0;line-height:1;vertical-align:top}
.colist td:not([class]):first-child img{max-width:none}
.colist td:not([class]):last-child{padding:.25em 0}
.thumb,.th{line-height:0;display:inline-block;border:4px solid #fff;box-shadow:0 0 0 1px #ddd}
.imageblock.left{margin:.25em .625em 1.25em 0}
.imageblock.right{margin:.25em 0 1.25em .625em}
.imageblock>.title{margin-bottom:0}
.imageblock.thumb,.imageblock.th{border-width:6px}
.imageblock.thumb>.title,.imageblock.th>.title{padding:0 .125em}
.image.left,.image.right{margin-top:.25em;margin-bottom:.25em;display:inline-block;line-height:0}
.image.left{margin-right:.625em}
.image.right{margin-left:.625em}
a.image{text-decoration:none;display:inline-block}
a.image object{pointer-events:none}
sup.footnote,sup.footnoteref{font-size:.875em;position:static;vertical-align:super}
sup.footnote a,sup.footnoteref a{text-decoration:none}
sup.footnote a:active,sup.footnoteref a:active{text-decoration:underline}
#footnotes{padding-top:.75em;padding-bottom:.75em;margin-bottom:.625em}
#footnotes hr{width:20%;min-width:6.25em;margin:-.25em 0 .75em;border-width:1px 0 0}
#footnotes .footnote{padding:0 .375em 0 .225em;line-height:1.3334;font-size:.875em;margin-left:1.2em;margin-bottom:.2em}
#footnotes .footnote a:first-of-type{font-weight:bold;text-decoration:none;margin-left:-1.05em}
#footnotes .footnote:last-of-type{margin-bottom:0}
#content #footnotes{margin-top:-.625em;margin-bottom:0;padding:.75em 0}
.gist .file-data>table{border:0;background:#fff;width:100%;margin-bottom:0}
.gist .file-data>table td.line-data{width:99%}
div.unbreakable{page-break-inside:avoid}
.big{font-size:larger}
.small{font-size:smaller}
.underline{text-decoration:underline}
.overline{text-decoration:overline}
.line-through{text-decoration:line-through}
.aqua{color:#00bfbf}
.aqua-background{background:#00fafa}
.black{color:#000}
.black-background{background:#000}
.blue{color:#0000bf}
.blue-background{background:#0000fa}
.fuchsia{color:#bf00bf}
.fuchsia-background{background:#fa00fa}
.gray{color:#606060}
.gray-background{background:#7d7d7d}
.green{color:#006000}
.green-background{background:#007d00}
.lime{color:#00bf00}
.lime-background{background:#00fa00}
.maroon{color:#600000}
.maroon-background{background:#7d0000}
.navy{color:#000060}
.navy-background{background:#00007d}
.olive{color:#606000}
.olive-background{background:#7d7d00}
.purple{color:#600060}
.purple-background{background:#7d007d}
.red{color:#bf0000}
.red-background{background:#fa0000}
.silver{color:#909090}
.silver-background{background:#bcbcbc}
.teal{color:#006060}
.teal-background{background:#007d7d}
.white{color:#bfbfbf}
.white-background{background:#fafafa}
.yellow{color:#bfbf00}
.yellow-background{background:#fafa00}
span.icon>.fa{cursor:default}
a span.icon>.fa{cursor:inherit}
.admonitionblock td.icon [class^="fa icon-"]{font-size:2.5em;text-shadow:1px 1px 2px rgba(0,0,0,.5);cursor:default}
.admonitionblock td.icon .icon-note::before{content:"\f05a";color:#19407c}
.admonitionblock td.icon .icon-tip::before{content:"\f0eb";text-shadow:1px 1px 2px rgba(155,155,0,.8);color:#111}
.admonitionblock td.icon .icon-warning::before{content:"\f071";color:#bf6900}
.admonitionblock td.icon .icon-caution::before{content:"\f06d";color:#bf3400}
.admonitionblock td.icon .icon-important::before{content:"\f06a";color:#bf0000}
.conum[data-value]{display:inline-block;color:#fff!important;background:rgba(0,0,0,.8);border-radius:50%;text-align:center;font-size:.75em;width:1.67em;height:1.67em;line-height:1.67em;font-family:"Open Sans","DejaVu Sans",sans-serif;font-style:normal;font-weight:bold}
.conum[data-value] *{color:#fff!important}
.conum[data-value]+b{display:none}
.conum[data-value]::after{content:attr(data-value)}
pre .conum[data-value]{position:relative;top:-.125em}
b.conum *{color:inherit!important}
.conum:not([data-value]):empty{display:none}
dt,th.tableblock,td.content,div.footnote{text-rendering:optimizeLegibility}
h1,h2,p,td.content,span.alt,summary{letter-spacing:-.01em}
p strong,td.content strong,div.footnote strong{letter-spacing:-.005em}
p,blockquote,dt,td.content,span.alt,summary{font-size:1.0625rem}
p{margin-bottom:1.25rem}
.sidebarblock p,.sidebarblock dt,.sidebarblock td.content,p.tableblock{font-size:1em}
.exampleblock>.content{background:#fffef7;border-color:#e0e0dc;box-shadow:0 1px 4px #e0e0dc}
.print-only{display:none!important}
@page{margin:1.25cm .75cm}
@media print{*{box-shadow:none!important;text-shadow:none!important}
html{font-size:80%}
a{color:inherit!important;text-decoration:underline!important}
a.bare,a[href^="#"],a[href^="mailto:"]{text-decoration:none!important}
a[href^="http:"]:not(.bare)::after,a[href^="https:"]:not(.bare)::after{content:"(" attr(href) ")";display:inline-block;font-size:.875em;padding-left:.25em}
abbr[title]{border-bottom:1px dotted}
abbr[title]::after{content:" (" attr(title) ")"}
pre,blockquote,tr,img,object,svg{page-break-inside:avoid}
thead{display:table-header-group}
svg{max-width:100%}
p,blockquote,dt,td.content{font-size:1em;orphans:3;widows:3}
h2,h3,#toctitle,.sidebarblock>.content>.title{page-break-after:avoid}
#header,#content,#footnotes,#footer{max-width:none}
#toc,.sidebarblock,.exampleblock>.content{background:none!important}
#toc{border-bottom:1px solid #dddddf!important;padding-bottom:0!important}
body.book #header{text-align:center}
body.book #header>h1:first-child{border:0!important;margin:2.5em 0 1em}
body.book #header .details{border:0!important;display:block;padding:0!important}
body.book #header .details span:first-child{margin-left:0!important}
body.book #header .details br{display:block}
body.book #header .details br+span::before{content:none!important}
body.book #toc{border:0!important;text-align:left!important;padding:0!important;margin:0!important}
body.book #toc,body.book #preamble,body.book h1.sect0,body.book .sect1>h2{page-break-before:always}
.listingblock code[data-lang]::before{display:block}
#footer{padding:0 .9375em}
.hide-on-print{display:none!important}
.print-only{display:block!important}
.hide-for-print{display:none!important}
.show-for-print{display:inherit!important}}
@media amzn-kf8,print{#header>h1:first-child{margin-top:1.25rem}
.sect1{padding:0!important}
.sect1+.sect1{border:0}
#footer{background:none}
#footer-text{color:rgba(0,0,0,.6);font-size:.9em}}
@media amzn-kf8{#header,#content,#footnotes,#footer{padding:0}}
</style>
</head>
<body class="article toc2 toc-left">
<div id="header">
<h1>Boost.IO</h1>
<div class="details">
<span id="author" class="author">Daryle Walker, Beman Dawes, Glen Joseph Fernandes &lt;glenjofe@gmail.com&gt;</span><br>
</div>
<div id="toc" class="toc2">
<div id="toctitle">Table of Contents</div>
<ul class="sectlevel1">
<li><a href="#io_state_savers_boostioios_state_hpp">IO State Savers, &lt;boost/io/ios_state.hpp&gt;</a>
<ul class="sectlevel2">
<li><a href="#description">Description</a></li>
<li><a href="#rationale">Rationale</a></li>
<li><a href="#header_synopsis">Header Synopsis</a></li>
<li><a href="#savers_for_basic_standard_attributes">Savers for Basic Standard Attributes</a></li>
<li><a href="#savers_for_advanced_standard_attributes">Savers for Advanced Standard Attributes</a></li>
<li><a href="#savers_for_user_defined_attributes">Savers for User-Defined Attributes</a></li>
<li><a href="#example">Example</a></li>
<li><a href="#credits">Credits</a></li>
<li><a href="#history">History</a></li>
</ul>
</li>
<li><a href="#quoted_manipulators_boostioquoted_hpp">Quoted Manipulators, &lt;boost/io/quoted.hpp&gt;</a>
<ul class="sectlevel2">
<li><a href="#introduction">Introduction</a></li>
<li><a href="#header_synopsis_2">Header synopsis</a></li>
<li><a href="#acknowledgements">Acknowledgements</a></li>
</ul>
</li>
<li><a href="#delimited_iterators_boostioostream_joiner_hpp">Delimited Iterators, &lt;boost/io/ostream_joiner.hpp&gt;</a>
<ul class="sectlevel2">
<li><a href="#description_2">Description</a></li>
<li><a href="#example_2">Example</a></li>
<li><a href="#reference">Reference</a></li>
<li><a href="#acknowledgments">Acknowledgments</a></li>
</ul>
</li>
<li><a href="#insert_formatted_output_boostioostream_put_hpp">Insert Formatted Output, &lt;boost/io/ostream_put.hpp&gt;</a>
<ul class="sectlevel2">
<li><a href="#description_3">Description</a></li>
<li><a href="#example_3">Example</a></li>
<li><a href="#reference_2">Reference</a></li>
<li><a href="#acknowledgments_2">Acknowledgments</a></li>
</ul>
</li>
<li><a href="#null_streams_boostionullstream_hpp">Null Streams, &lt;boost/io/nullstream.hpp&gt;</a>
<ul class="sectlevel2">
<li><a href="#description_4">Description</a></li>
<li><a href="#example_4">Example</a></li>
<li><a href="#reference_3">Reference</a></li>
<li><a href="#acknowledgments_3">Acknowledgments</a></li>
</ul>
</li>
<li><a href="#copyright_and_license">Copyright and License</a></li>
</ul>
</div>
</div>
<div id="content">
<div id="preamble">
<div class="sectionbody">
<div class="paragraph">
<p>This library contains various utilities for the standard I/O library.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="io_state_savers_boostioios_state_hpp">IO State Savers, &lt;boost/io/ios_state.hpp&gt;</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="description">Description</h3>
<div class="paragraph">
<p>The header <code>&lt;boost/io/ios_state.hpp&gt;</code> covers saving the stream state of objects
in the C&#43;&#43; IOStreams system.</p>
</div>
</div>
<div class="sect2">
<h3 id="rationale">Rationale</h3>
<div class="paragraph">
<p>Sometimes a certain value has to change only for a limited scope. Saver classes
save a copy of the current state of some object (or an aspect of an object),
and reset the object&#8217;s state at destruction time, undoing any change the object
may have gone through.</p>
</div>
<div class="paragraph">
<p>The saver class strategy is helpful when using I/O stream objects. Manipulator
objects can change some aspect of a stream during input or output. The state
changed by the manipulator usually sticks to its new value after the I/O
transaction. This can be a problem if manipulators are used in a function that
is not supposed to externally change a stream&#8217;s state.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">#include &lt;ostream&gt;
#include &lt;ios&gt;

void hex_my_byte(std::ostream&amp; os, char byte)
{
    os &lt;&lt; std::hex &lt;&lt; static_cast&lt;unsigned&gt;(byte);
}</code></pre>
</div>
</div>
<div class="paragraph">
<p>The <code>os</code> stream will retain its new hexadecimal printing mode after the call to
<code>hex_my_byte</code>. The stream&#8217;s printing mode can be saved and restored with manual
calls to the stream&#8217;s state inspecting and mutating member functions. The
manual method becomes unwieldy if the main functionality is complex and/or
needs to be exception safe. A saver class can implement the better
"resource acquisition is initialization" strategy.</p>
</div>
<div class="paragraph">
<p>See the example below for better code, using saver classes.</p>
</div>
</div>
<div class="sect2">
<h3 id="header_synopsis">Header Synopsis</h3>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">namespace boost {
namespace io {

class ios_flags_saver;
class ios_precision_saver;
class ios_width_saver;
class ios_base_all_saver;

template&lt;class Ch, class Tr = std::char_traits&lt;Ch&gt; &gt;
class basic_ios_iostate_saver;

template&lt;class Ch, class Tr = std::char_traits&lt;Ch&gt; &gt;
class basic_ios_exception_saver;

template&lt;class Ch, class Tr = std::char_traits&lt;Ch&gt; &gt;
class basic_ios_tie_saver;

template&lt;class Ch, class Tr = std::char_traits&lt;Ch&gt; &gt;
class basic_ios_rdbuf_saver;

template&lt;class Ch, class Tr = std::char_traits&lt;Ch&gt; &gt;
class basic_ios_fill_saver;

template&lt;class Ch, class Tr = std::char_traits&lt;Ch&gt; &gt;
class basic_ios_locale_saver;

template&lt;class Ch, class Tr = std::char_traits&lt;Ch&gt; &gt;
class basic_ios_all_saver;

typedef basic_ios_iostate_saver&lt;char&gt;      ios_iostate_saver;
typedef basic_ios_iostate_saver&lt;wchar_t&gt;   wios_iostate_saver;
typedef basic_ios_exception_saver&lt;char&gt;    ios_exception_saver;
typedef basic_ios_exception_saver&lt;wchar_t&gt; wios_exception_saver;
typedef basic_ios_tie_saver&lt;char&gt;          ios_tie_saver;
typedef basic_ios_tie_saver&lt;wchar_t&gt;       wios_tie_saver;
typedef basic_ios_rdbuf_saver&lt;char&gt;        ios_rdbuf_saver;
typedef basic_ios_rdbuf_saver&lt;wchar_t&gt;     wios_rdbuf_saver;
typedef basic_ios_fill_saver&lt;char&gt;         ios_fill_saver;
typedef basic_ios_fill_saver&lt;wchar_t&gt;      wios_fill_saver;
typedef basic_ios_locale_saver&lt;char&gt;       ios_locale_saver;
typedef basic_ios_locale_saver&lt;wchar_t&gt;    wios_locale_saver;
typedef basic_ios_all_saver&lt;char&gt;          ios_all_saver;
typedef basic_ios_all_saver&lt;wchar_t&gt;       wios_all_saver;

class ios_iword_saver;
class ios_pword_saver;
class ios_all_word_saver;

} // io
} // boost</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="savers_for_basic_standard_attributes">Savers for Basic Standard Attributes</h3>
<div class="paragraph">
<p>The basic saver classes have this format:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">class saver {
public:
    typedef std::ios_base state_type;
    typedef <code>implementation_defined</code> aspect_type;

    explicit saver(state_type&amp; s);
    saver(state_type&amp; s, const aspect_type&amp; new_value);
    ~saver();

    void restore();
};</code></pre>
</div>
</div>
<div class="paragraph">
<p>The <code>state_type</code> is the IOStreams base class <code>std::ios_base</code>. The user would
usually place an actual input, output, or combined stream object for the
state-type parameter, and not a base class object. The first constructor takes
a stream object and saves a reference to the stream and the current value of a
particular stream attribute. The second constructor works like the first, and
uses its second argument to change the stream&#8217;s attribute to the new
<code>aspect_type</code> value given. The destructor restores the stream&#8217;s attribute to
the saved value. The restoration can be activated early (and often) with the
<code>restore</code> member function.</p>
</div>
<table class="tableblock frame-all grid-all stretch">
<caption class="title">Table 1. Basic IOStreams State Saver Classes</caption>
<colgroup>
<col style="width: 20%;">
<col style="width: 20%;">
<col style="width: 20%;">
<col style="width: 20%;">
<col style="width: 20%;">
</colgroup>
<thead>
<tr>
<th class="tableblock halign-left valign-top">Class</th>
<th class="tableblock halign-left valign-top">Saved Attribute</th>
<th class="tableblock halign-left valign-top">Attribute Type</th>
<th class="tableblock halign-left valign-top">Reading Method</th>
<th class="tableblock halign-left valign-top">Writing Method</th>
</tr>
</thead>
<tbody>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>ios_flags_saver</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Format control flags</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>std::ios_base::fmtflags</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>flags</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>flags</code></p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>ios_precision_saver</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Number of digits to print after decimal point</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>std::streamsize</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>precision</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>precision</code></p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>ios_width_saver</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Minimum field width for printing objects</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>std::streamsize</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>width</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>width</code></p></td>
</tr>
</tbody>
</table>
</div>
<div class="sect2">
<h3 id="savers_for_advanced_standard_attributes">Savers for Advanced Standard Attributes</h3>
<div class="paragraph">
<p>The saver class templates have this format:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">template&lt;class Ch, class Tr&gt;
class saver {
public:
    typedef std::basic_ios&lt;Ch, Tr&gt; state_type;
    typedef <code>implementation-defined</code> aspect_type;

    explicit saver(state_type&amp; s);
    saver(state_type&amp; s, const aspect_type&amp; new_value);
    ~saver();

    void restore();
};</code></pre>
</div>
</div>
<div class="paragraph">
<p>The <code>state_type</code> is a version of the IOStreams base class template
<code>std::basic_ios&lt;Ch, Tr&gt;</code>, where <code>Ch</code> is a character type and <code>Tr</code> is a
character traits class. The user would usually place an actual input,
output, or combined stream object for the state-type parameter, and not a base
class object. The first constructor takes a stream object and saves a reference
to the stream and the current value of a particular stream attribute. The
second constructor works like the first, and uses its second argument to change
the stream&#8217;s attribute to the new <code>aspect_type</code> value given. The destructor
restores the stream&#8217;s attribute to the saved value. The restoration can be
activated early (and often) with the <code>restore</code> member function.</p>
</div>
<table class="tableblock frame-all grid-all stretch">
<caption class="title">Table 2. Advanced IOStreams State Saver Class Templates</caption>
<colgroup>
<col style="width: 20%;">
<col style="width: 20%;">
<col style="width: 20%;">
<col style="width: 20%;">
<col style="width: 20%;">
</colgroup>
<thead>
<tr>
<th class="tableblock halign-left valign-top">Class</th>
<th class="tableblock halign-left valign-top">Saved Attribute</th>
<th class="tableblock halign-left valign-top">Attribute Type</th>
<th class="tableblock halign-left valign-top">Reading Method</th>
<th class="tableblock halign-left valign-top">Writing Method</th>
</tr>
</thead>
<tbody>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>basic_ios_iostate_saver&lt;Ch, Tr&gt;</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Failure state of the stream [1], [2]</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>std::ios_base::iostate</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>rdstate</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>clear</code></p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>basic_ios_exception_saver&lt;Ch, Tr&gt;</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Which failure states trigger an exception [1]</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>std::ios_base::iostate</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>exceptions</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>exceptions</code></p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>basic_ios_tie_saver&lt;Ch, Tr&gt;</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Output stream synchronized with the stream</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>std::basic_ostream&lt;Ch, Tr&gt;*</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>tie</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>tie</code></p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>basic_ios_rdbuf_saver&lt;Ch, Tr&gt;</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Stream buffer associated with the stream [2]</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>std::basic_streambuf&lt;Ch, Tr&gt;*</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>rdbuf</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>rdbuf</code></p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>basic_ios_fill_saver&lt;Ch, Tr&gt;</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Character used to pad oversized field widths</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>Ch</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>fill</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>fill</code></p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>basic_ios_locale_saver&lt;Ch, Tr&gt;</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Locale information associated with the stream [3]</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>std::locale</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>getloc</code> (from <code>std::ios_base</code>)</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>imbue</code> (from <code>std::basic_ios&lt;Ch, Tr&gt;</code>)</p></td>
</tr>
</tbody>
</table>
<div class="sect3">
<h4 id="notes">Notes</h4>
<div class="olist arabic">
<ol class="arabic">
<li>
<p>When the failure state flags and/or the failure state exception watching
flags are changed, an exception is thrown if a match occurs among the two sets
of flags. This could mean that the constructor or destructor of these class
templates may throw.</p>
</li>
<li>
<p>When the associated stream buffer is changed, the stream&#8217;s failure state set
is reset to "good" if the given stream buffer&#8217;s address is non-NULL, but the
"bad" failure state is set if that address is NULL. This means that a saved
failure state of "good" may be restored as "bad" if the stream is stripped of
an associated stream buffer. Worse, given a NULL stream buffer address, an
exception is thrown if the "bad" failure state is being watched. This could
mean that the constructor or destructor of these class templates may throw.</p>
</li>
<li>
<p>The saver for the locale uses the <code>std::basic_ios&lt;Ch, Tr&gt;</code> class to extract
their information, although it could have used the functionality in
<code>std::ios_base</code>. The problem is that the versions of the needed member
functions in <code>ios_base</code> are not polymorphically related to the ones in
<code>basic_ios</code>. The stream classes that will be used with the saver classes should
use the versions of the member functions closest to them by inheritance, which
means the ones in <code>basic_ios</code>.</p>
</li>
</ol>
</div>
</div>
</div>
<div class="sect2">
<h3 id="savers_for_user_defined_attributes">Savers for User-Defined Attributes</h3>
<div class="paragraph">
<p>There are three class (templates) for combined attribute savers. The
<code>ios_base_all_saver</code> saver class combines the functionality of all the basic
attribute saver classes. It has a constructor that takes the stream to have its
state preserved. The <code>basic_ios_all_saver</code> combines the functionality of all
the advanced attribute saver class templates and the combined basic attribute
saver class. It has a constructor that takes the stream to have its state
preserved. The <code>ios_all_word_saver</code> saver class combines the saver classes that
preserve user-defined formatting information. Its constructor takes the stream
to have its attributes saved and the index of the user-defined attributes. The
destructor for each class restores the saved state. Restoration can be
activated early (and often) for a class with the restore member function.</p>
</div>
</div>
<div class="sect2">
<h3 id="example">Example</h3>
<div class="paragraph">
<p>The code used in the rationale can be improved at two places. The printing
function could use a saver around the code that changes the formatting state.
Or the calling function can surround the call with a saver. Or both can be
done, especially if the user does not know if the printing function uses a
state saver. If the user wants a series of changes back and forth, without
surrounding each change within a separate block, the restore member function
can be called between each trial.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">#include &lt;boost/io/ios_state.hpp&gt;
#include &lt;ios&gt;
#include &lt;iostream&gt;
#include &lt;ostream&gt;

void new_hex_my_byte(std::ostream&amp; os, char byte)
{
    boost::io::ios_flags_saver ifs(os);
    os &lt;&lt; std::hex &lt;&lt; static_cast&lt;unsigned&gt;(byte);
}

int main()
{
    // ...
    {
        boost::io::ios_all_saver ias(std::cout);
        new_hex_my_byte(std::cout, 'A');
    }
    // ...
    {
        boost::io::ios_all_saver ias(std::cerr);
        new_hex_my_byte(std::cerr, 'b');
        ias.restore();
        new_hex_my_byte(std::cerr, 'C');
    }
    // ...
}</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="credits">Credits</h3>
<div class="sect3">
<h4 id="daryle_walker">Daryle Walker</h4>
<div class="paragraph">
<p>Started the library. Contributed the initial versions of the format flags,
precision, width, and user-defined format flags saver classes. Contributed the
initial versions of the success state, success state exception flags, output
stream tie, stream buffer, character fill, and locale saver class templates.
Contributed the combined attribute classes and class template. Contributed the
test file <code>ios_state_test.cpp</code>.</p>
</div>
</div>
</div>
<div class="sect2">
<h3 id="history">History</h3>
<div class="sect3">
<h4 id="20_dec_2019">20 Dec 2019</h4>
<div class="paragraph">
<p>Glen Fernandes made all the saver classes non-copyable.</p>
</div>
</div>
<div class="sect3">
<h4 id="28_feb_2005">28 Feb 2005</h4>
<div class="paragraph">
<p>Daryle Walker added the restore member functions, based on suggestions by
Gennadiy Rozental and Rob Stewart.</p>
</div>
</div>
<div class="sect3">
<h4 id="13_mar_2002">13 Mar 2002</h4>
<div class="paragraph">
<p>Daryle Walker implemented the initial version.</p>
</div>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="quoted_manipulators_boostioquoted_hpp">Quoted Manipulators, &lt;boost/io/quoted.hpp&gt;</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="introduction">Introduction</h3>
<div class="paragraph">
<p>C++ Standard library stream I/O for strings that contain embedded spaces can
produce unexpected results. For example,</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">std::stringstream ss;
std::string original = "fooled you";
std::string roundtrip;

ss &lt;&lt; original;
ss &gt;&gt; roundtrip;

std::cout &lt;&lt; original;   // outputs: fooled you
std::cout &lt;&lt; roundtrip; // outputs: fooled

assert(original == roundtrip); // assert will fire</code></pre>
</div>
</div>
<div class="paragraph">
<p>The Boost quoted stream I/O manipulator places delimiters, defaulted to the
double-quote ("), around strings on output, and strips off the delimiters on
input. This ensures strings with embedded spaces round-trip as desired. For
example,</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">std::stringstream ss;
std::string original = "fooled you";
std::string roundtrip;

ss &lt;&lt; quoted(original);
ss &gt;&gt; quoted(roundtrip);

std::cout &lt;&lt; quoted(original); // outputs: "fooled you"
std::cout &lt;&lt; roundtrip;       // outputs: fooled you

assert(original == roundtrip); // assert will not fire</code></pre>
</div>
</div>
<div class="paragraph">
<p>If the string contains the delimiter character, on output that character will
be preceded by an escape character, as will the escape character itself:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">std::cout &lt;&lt; quoted("'Jack &amp; Jill'", '&amp;', '\''); // outputs: '&amp;'Jack &amp;&amp; Jill&amp;''</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="header_synopsis_2">Header synopsis</h3>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">namespace boost {
namespace io {

template&lt;class Char, class Traits, class Alloc&gt;
<code>unspecified-type1</code>
quoted(const std::basic_string&lt;Char, Traits, Alloc&gt;&amp; string,
       Char escape='\\', Char delim='\"');

template&lt;class Char&gt;
<code>unspecified-type2</code>
quoted(const Char* string, Char escape='\\', Char delim='\"');

template&lt;class Char, class Traits, class Alloc&gt;
<code>unspecified-type3</code>
quoted(std::basic_string&lt;Char, Traits, Alloc&gt;&amp; string,
       Char escape='\\', Char delim='\"');

} // io
} // boost</code></pre>
</div>
</div>
<div class="paragraph">
<p><strong>unspecified-type1</strong>, <strong>unspecified-type2</strong>, and <strong>unspecified-type3</strong> are
implementation supplied types with implementation supplied <code>operator&lt;&lt;</code>:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">template&lt;class Char, class Traits&gt;
std::basic_ostream&lt;Char, Traits&gt;&amp;
operator&lt;&lt;(std::basic_ostream&lt;Char, Traits&gt;&amp; os,
           const <code>unspecified-typeN</code>&amp; proxy);</code></pre>
</div>
</div>
<div class="dlist">
<dl>
<dt class="hdlist1">Effects</dt>
<dd>
<p>Inserts characters into <code>os</code>:</p>
<div class="ulist">
<ul>
<li>
<p><code>delim</code></p>
</li>
<li>
<p>Each character in <code>string</code>. If the character to be output is equal to
<code>escape</code> or <code>delim</code>, as determined by <code>operator==</code>, first output <code>escape</code>.</p>
</li>
<li>
<p><code>delim</code></p>
</li>
</ul>
</div>
</dd>
<dt class="hdlist1">Remarks</dt>
<dd>
<p><code>string</code>, <code>escape</code>, and <code>delim</code> have the type and value of the
corresponding arguments of the call to the <code>quoted</code> function that constructed
<code>proxy</code>.</p>
</dd>
<dt class="hdlist1">Returns</dt>
<dd>
<p><code>os</code>.</p>
</dd>
</dl>
</div>
<div class="paragraph">
<p><strong>unspecified-type3</strong> is an implementation supplied type with an implementation
supplied <code>operator&gt;&gt;</code>:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">template&lt;class Char, class Traits&gt;
std::basic_istream&lt;Char, Traits&gt;&amp;
operator&gt;&gt;(std::basic_istream&lt;Char, Traits&gt;&amp; is,
           const <code>unspecified-type3</code>&amp; proxy);</code></pre>
</div>
</div>
<div class="dlist">
<dl>
<dt class="hdlist1">Effects</dt>
<dd>
<p>Extracts characters from <code>os</code>:</p>
<div class="ulist">
<ul>
<li>
<p>If the first character extracted is equal to <code>delim</code>, as determined by
<code>operator==</code>, then:</p>
<div class="ulist">
<ul>
<li>
<p>Turn off the <code>skipws</code> flag.</p>
</li>
<li>
<p><code>string.clear()</code></p>
</li>
<li>
<p>Until an unescaped <code>delim</code> character is reached or <code>is.not_good()</code>, extract
characters from <code>os</code> and append them to string, except that if an escape is
reached, ignore it and append the next character to string.</p>
</li>
<li>
<p>Discard the final <code>delim</code> character.</p>
</li>
<li>
<p>Restore the <code>skipws</code> flag to its original value.</p>
</li>
</ul>
</div>
</li>
<li>
<p>Otherwise, <code>os &gt;&gt; string</code>.</p>
</li>
</ul>
</div>
</dd>
<dt class="hdlist1">Remarks</dt>
<dd>
<p><code>string</code>, <code>escape</code>, and <code>delim</code> have the type and value of the
corresponding arguments of the call to the <code>quoted</code> function that constructed
<code>proxy</code>.</p>
</dd>
<dt class="hdlist1">Returns</dt>
<dd>
<p><code>is</code>.</p>
</dd>
</dl>
</div>
</div>
<div class="sect2">
<h3 id="acknowledgements">Acknowledgements</h3>
<div class="paragraph">
<p>The <code>quoted()</code> stream manipulator emerged from discussions on the Boost
developers mailing list. Participants included Beman Dawes, Rob Stewart,
Alexander Lamaison, Eric Niebler, Vicente Botet, Andrey Semashev,
Phil Richards, and Rob Murray. Eric Niebler&#8217;s suggestions provided the basis
for the name and form of the templates.</p>
</div>
<div class="paragraph">
<p>Beman Dawes started the implementation of <code>quoted()</code> as a private detail
header. Glen Fernandes updated the implementation and also made it public.</p>
</div>
<div class="paragraph">
<p>Glen Fernandes corrected the implementation to properly account for stream
width and fill, and optimized it to write directly to the stream buffer.</p>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="delimited_iterators_boostioostream_joiner_hpp">Delimited Iterators, &lt;boost/io/ostream_joiner.hpp&gt;</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="description_2">Description</h3>
<div class="paragraph">
<p>The header <code>&lt;boost/io/ostream_joiner.hpp&gt;</code> provides the class template
<code>boost::io::ostream_joiner</code> which is an output iterator that writes objects to
a <code>std::basic_ostream</code> separated by a delimiter. It is an implementation of
the Library Fundamentals TS <code>std::ostream_joiner</code> which supports C&#43;&#43;03 and
higher.</p>
</div>
</div>
<div class="sect2">
<h3 id="example_2">Example</h3>
<div class="paragraph">
<p>The following program writes the contents of a vector to standard output, with
each element separated by a comma.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">#include &lt;boost/io/ostream_joiner.hpp&gt;
#include &lt;algorithm&gt;
#include &lt;iostream&gt;
#include &lt;vector&gt;

int main()
{
    std::vector&lt;int&gt; v;
    v.push_back(2);
    v.push_back(4);
    v.push_back(6);
    v.push_back(8);
    std::copy(v.begin(), v.end(), boost::make_ostream_joiner(std::cout, ','));
}</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="reference">Reference</h3>
<div class="sect3">
<h4 id="header_synopsis_3">Header Synopsis</h4>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">namespace boost {
namespace io {

template&lt;class Delim, class Char = char,
    class Traits = std::char_traits&lt;Char&gt; &gt;
class ostream_joiner {
public:
    typedef Char char_type;
    typedef Traits traits_type;
    typedef std::basic_ostream&lt;Char, Traits&gt; ostream_type;
    typedef std::output_iterator_tag iterator_category;
    typedef void value_type;
    typedef void difference_type;
    typedef void pointer;
    typedef void reference;

    ostream_joiner(ostream_type&amp; output, const Delim&amp; delim);
    ostream_joiner(ostream_type&amp; output, Delim&amp;&amp; delim);

    template&lt;class T&gt;
    ostream_joiner&amp; operator=(const T&amp; value);

    ostream_joiner&amp; operator*() noexcept;
    ostream_joiner&amp; operator++() noexcept;
    ostream_joiner&amp; operator++(int) noexcept;
};

template&lt;class Char, class Traits, class Delim&gt;
ostream_joiner&lt;std::decay_t&lt;Delim&gt;, Char, Traits&gt;
make_ostream_joiner(std::basic_ostream&lt;Char, Traits&gt;&amp; output, Delim&amp;&amp; delim);

} // io
} // boost</code></pre>
</div>
</div>
</div>
<div class="sect3">
<h4 id="constructors">Constructors</h4>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">ostream_joiner(ostream_type&amp; output, const Delim&amp; delim);</code></pre>
</div>
</div>
<div class="dlist specification">
<dl>
<dt class="hdlist1">EFfects</dt>
<dd>
<p>Initializes the stored reference to the stream with
<code>std::addressof(output)</code> and the stored delimiter with <code>delim</code>.</p>
</dd>
</dl>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">ostream_joiner(ostream_type&amp; output, Delim&amp;&amp; delim);</code></pre>
</div>
</div>
<div class="dlist specification">
<dl>
<dt class="hdlist1">EFfects</dt>
<dd>
<p>Initializes the stored reference to the stream with
<code>std::addressof(output)</code> and the stored delimiter with <code>std::move(delim)</code>.</p>
</dd>
</dl>
</div>
</div>
<div class="sect3">
<h4 id="member_functions">Member functions</h4>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">template&lt;class T&gt;
ostream_joiner&amp; operator=(const T&amp; value);</code></pre>
</div>
</div>
<div class="dlist specification">
<dl>
<dt class="hdlist1">Effects</dt>
<dd>
<p>If the is the first call to this member function, write the stored
delimiter to the stored stream reference. Writes <code>value</code> to the stored stream
reference.</p>
</dd>
<dt class="hdlist1">Returns</dt>
<dd>
<p><code>*this</code>.</p>
</dd>
</dl>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">ostream_joiner&amp; operator*() noexcept;</code></pre>
</div>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">ostream_joiner&amp; operator++() noexcept;</code></pre>
</div>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">ostream_joiner&amp; operator++(int) noexcept;</code></pre>
</div>
</div>
<div class="dlist specification">
<dl>
<dt class="hdlist1">Returns</dt>
<dd>
<p><code>*this</code>.</p>
</dd>
</dl>
</div>
</div>
<div class="sect3">
<h4 id="free_functions">Free functions</h4>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">template&lt;class Char, class Traits, class Delim&gt;
ostream_joiner&lt;decay_t&lt;Delim&gt;, Char, Traits&gt;
make_ostream_joiner(std::basic_ostream&lt;Char, Traits&gt;&amp; output, Delim&amp;&amp; delim);</code></pre>
</div>
</div>
<div class="dlist specification">
<dl>
<dt class="hdlist1">Returns</dt>
<dd>
<p><code>ostream_joiner&lt;std::decay_t&lt;Delim&gt;, Char, Traits&gt;(output,
std::forward&lt;Delim&gt;(delim))</code>.</p>
</dd>
</dl>
</div>
</div>
</div>
<div class="sect2">
<h3 id="acknowledgments">Acknowledgments</h3>
<div class="paragraph">
<p>Glen Fernandes implemented <code>ostream_joiner</code> and <code>make_ostream_joiner</code>.</p>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="insert_formatted_output_boostioostream_put_hpp">Insert Formatted Output, &lt;boost/io/ostream_put.hpp&gt;</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="description_3">Description</h3>
<div class="paragraph">
<p>The header <code>&lt;boost/io/ostream_put.hpp&gt;</code> provides the function template
<code>boost::io::ostream_put</code> for formatted output that satisfies the requirements
of [ostream.formatted.reqmts].</p>
</div>
</div>
<div class="sect2">
<h3 id="example_3">Example</h3>
<div class="paragraph">
<p>The inserter for class template <code>basic_string_view</code> could be implemented as
follows:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">template&lt;class charT, class traits&gt;
std::basic_ostream&lt;charT, traits&gt;&amp;
operator&lt;&lt;(std::basic_ostream&lt;charT, traits&gt;&amp; os,
    const basic_string_view&lt;charT, traits&gt;&amp; str)
{
    return boost::io::ostream_put(os, str.data(), str.size());
}</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="reference_2">Reference</h3>
<div class="sect3">
<h4 id="header_synopsis_4">Header Synopsis</h4>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">namespace boost {
namespace io {

template&lt;class charT, class traits&gt;
std::basic_ostream&lt;charT, traits&gt;&amp;
ostream_put(std::basic_ostream&lt;charT, traits&gt;&amp; os,
    const charT* data, std::size_t size);

} // io
} // boost</code></pre>
</div>
</div>
</div>
<div class="sect3">
<h4 id="free_functions_2">Free functions</h4>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">template&lt;class charT, class traits&gt;
std::basic_ostream&lt;charT, traits&gt;&amp;
ostream_put(std::basic_ostream&lt;charT, traits&gt;&amp; os,
    const charT* data, std::size_t size);</code></pre>
</div>
</div>
<div class="dlist specification">
<dl>
<dt class="hdlist1">Effects</dt>
<dd>
<p>Behaves like a formatted inserter (as described in
[ostream.formatted.reqmts]) of <code>os</code>. Creates a character sequence <code>seq</code> of size
characters starting at <code>data</code>, each widened using <code>os.widen()</code>
([basic.ios.members]). Determines padding for <code>seq</code> as described in
[ostream.formatted.reqmts]. Inserts <code>seq</code> into <code>os</code>. Calls <code>width(0)</code>.</p>
</dd>
<dt class="hdlist1">Returns</dt>
<dd>
<p><code>os</code>.</p>
</dd>
</dl>
</div>
</div>
</div>
<div class="sect2">
<h3 id="acknowledgments_2">Acknowledgments</h3>
<div class="paragraph">
<p>Glen Fernandes updated the implementation of the <code>basic_string_ref</code> and
<code>basic_string_view</code> stream insertion operators to write directly to the
<code>basic_streambuf</code> and refactored that functionality into this common utility.</p>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="null_streams_boostionullstream_hpp">Null Streams, &lt;boost/io/nullstream.hpp&gt;</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="description_4">Description</h3>
<div class="paragraph">
<p>The header <code>&lt;boost/io/nullstream.hpp&gt;</code> provides the class template
<code>boost::io::basic_nullbuf</code> which is a null stream buffer and class template
<code>boost::io::basic_onullstream</code> which is a null stream.</p>
</div>
</div>
<div class="sect2">
<h3 id="example_4">Example</h3>
<div class="paragraph">
<p>The following program passes a null stream to a function.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">#include &lt;boost/io/ostream_joiner.hpp&gt;
#include &lt;fstream&gt;

void setup(std::ostream&amp; log);

int main(int argc, char* argv[])
{
    if (argc == 2) {
        std::ofstream file(argv[1]);
        setup(file);
    } else {
        boost::io::onullstream none;
        setup(none);
    }
}</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="reference_3">Reference</h3>
<div class="sect3">
<h4 id="header_synopsis_5">Header Synopsis</h4>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-cpp" data-lang="cpp">namespace boost {
namespace io {

template&lt;class CharT, class Traits = std::char_traits&lt;Char&gt; &gt;
class basic_nullbuf
    : public std::basic_streambuf&lt;CharT, Traits&gt; {
protected:
    typename Traits::int_type overflow(typename Traits::int_type c) override;

    std::streamsize xsputn(const CharT*, std::streamsize n) override;
};

template&lt;class CharT, class Traits = std::char_traits&lt;CharT&gt; &gt;
class basic_onullstream
    : public std::basic_ostream&lt;CharT, Traits&gt; {
public:
    basic_onullstream();
};

typedef basic_onullstream&lt;char&gt; onullstream;
typedef basic_onullstream&lt;wchar_t&gt; wonullstream;

} // io
} // boost</code></pre>
</div>
</div>
</div>
</div>
<div class="sect2">
<h3 id="acknowledgments_3">Acknowledgments</h3>
<div class="paragraph">
<p>Glen Fernandes implemented <code>basic_nullbuf</code> and <code>basic_onullstream</code>.</p>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="copyright_and_license">Copyright and License</h2>
<div class="sectionbody">
<div class="ulist">
<ul>
<li>
<p>Copyright 2002 Daryle Walker</p>
</li>
<li>
<p>Copyright 2002, 2006, 2007, 2009, 2010 Beman Dawes</p>
</li>
<li>
<p>Copyright 2019 Glen Joseph Fernandes</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>Distributed under the
<a href="http://www.boost.org/LICENSE_1_0.txt">Boost Software License, Version 1.0</a>.</p>
</div>
</div>
</div>
</div>
<div id="footer">
<div id="footer-text">
Last updated 2022-04-06 21:02:38 UTC
</div>
</div>
<style>
.specification {
margin-left: 2em;
}
</style>
</body>
</html>